The Science behind Taste and Appetite Understanding Why We Like What We Like

Once a year comes the Mid-Autumn Festival, and it's time to eat mooncakes.

After eating mooncakes for so many years, what flavors of mooncakes are there? Firstly, there are said to be nine major schools in the mooncake world [1]: Cantonese mooncakes, Suzhou mooncakes, Beijing-style mooncakes, Chaozhou mooncakes, Yunnan mooncakes, Shanxi mooncakes, Hainan mooncakes, Taiwan mooncakes, and Harbin mooncakes. Secondly, by flavor, there are classic ones like lotus seed paste, five-nut, red bean paste, egg yolk, and ham, and then there are all kinds of new flavors, only you can't think of it, basically there are no fruit mooncakes, rice wine mooncakes, lava mooncakes, ice cream mooncakes, milk crust mooncakes that can't be made, and even more like pepper beef, snail powder, crayfish, abalone, mango pomelo sago, and coconut milk coffee mooncakes, etc.

While being dazzled! Do you notice that the person who ate mooncakes with you back then, actually has changed their taste! And the 'white moonlight cake' in your heart has always been that one true love (lotus seed paste and egg yolk). Or perhaps you no longer like the taste you used to like, just like when I hated cilantro and durian as a child, but now it's really 'true love'!

Then start to seriously think, what aspects affect human beings' judgment of whether a food is delicious? Why do some people's tastes change significantly?

1. Where does the thought of 'I want to eat' come from?

Whether we want to eat a certain food is largely driven by the interaction of homeostatic control and reward signals.

Homeostatic control

Homeostatic control refers to regulating body parameters to maintain the balance of the internal environment of the body, such as body temperature, hunger, and thirst. The hypothalamus is a key regulator of energy homeostasis and is functionally connected to the striatum and cortical areas that are crucial for appetite control. The hypothalamus receives signals from all parts of the body, such as nutrient levels, intestinal satiety signals and fat tissue-related hormones, to judge the energy state through signals circulating or transmitted through vagus nerve fibers.

Reward signal

The reward system mainly operates in the limbic system of the brain and involves driving motivation to preferentially choose more palatable and energy-dense foods. There is a subtle balance between top-down regulation from the prefrontal cortex (a key area for cognitive control) and bottom-up regulation from the limbic reward pathway. The dopamine reward system plays the most prominent role in regulating appetite and motivational behavior. When seeing an appetizing food, whether it's an adult or a child, the visual-related brain regions and the reward-related regions (orbitofrontal cortex, parahippocampal gyrus and insula) will be enhanced, generating the urge to eat.

2. How does the feeling of 'quite delicious' come about?

When we eat food and feel it's quite delicious, generally speaking, it means that the interaction of taste, smell, trigeminal nerve and touch is transformed into perception and leads to descriptions such as sweet, bitter, salty, sour and umami in terms of taste [3]. In addition, it also includes some unique sensory experiences such as astringency, coolness and spiciness, etc.

Taste is generated due to the reaction of taste receptors in the oral cavity to chemicals in food. Studies have shown that the activity of α-amylase in saliva and the release amount of reducing sugars in saliva have a significant impact on the perception of starchy sweetness [4]. This explains that physiological conditions and metabolic activities will affect our experience of certain tastes.

And the ability of humans to distinguish subtle differences in food flavors mainly depends on retro-nasal odor [5]. Volatiles of food reach the posterior of the oral cavity and are transported through the nasal cavity by exhaled air to stimulate olfactory receptor neurons.

3. Will this 'feeling' ability change?

Since eating is triggered by many factors, including the visual and olfactory effects of food and personal memories, etc.; our favorite flavors will naturally also change along with changes in hormones, neurons and external stimuli in our bodies. The reasons for our taste changes include but are not limited to:

Getting older

The brain regions closely related to eating desire, such as the mesolimbic and prefrontal cortices, develop at different speeds. Therefore, it is normal for taste preferences to change significantly as one gets older. In studies on mammals, it is found that gene expression related to age in the hypothalamus changes significantly with age. The food intake in old age is reduced, but the expression of neuropeptide genes related to food intake is more vigorous [6].

In the infant period of humans, in addition to the instinctive preference for sweet and dislike for bitter, it is also affected by the mother's diet during pregnancy. After childhood, most still maintain a high preference for sweetness and are keen on high-salt foods, and then gradually decline after entering puberty [7]. Then as one gets older, the guidance of family diet will gradually take the main role. At the same time, considerations such as health, convenience, price, etc. will also begin to develop, and different eating habits will emerge. For example, as one gets older, high-calorie foods will be considered more delicious but less healthy [2].

Other factors

Mood and lifestyle changes can also significantly affect eating choices. Studies have shown that sadness leads people to be more willing to pay for unnecessary consumer goods and generate unhealthy food consumption [8]. At the same time, psychological stress is also closely related to eating desire. For example, being young, stressed, not obese and eating less when stressed may lead to a preference for salty foods (instead of sweet ones) [9]. In terms of lifestyle, such as staying up late will significantly change the hormone levels in the body, making us eat unconsciously more.

Suddenly remembering the scene of staying up late to work and then eating snacks and being seen by the big director while eating office mooncakes...

Summary

As the synonym of deliciousness, at the moment when mooncakes are dazzling, we should also be careful to hold our wallets! After all, we are not good at estimating probabilities and objective risks - overestimating our self-control ability and underestimating the health risks associated with the choices we make. Instead, we cheat in mental accounting: I ate too much today, but I will eat less tomorrow. Explained by the time discounting of future conditions of behavioral economists [8], we tend to choose the current enjoyment (the mooncakes eaten) rather than what we hope for later (slim and healthy). So mooncakes are delicious, but don't eat too much either! ~

Stop talking, eat another small piece of mooncake...

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This article is from the WeChat public account: WeChat public account (ID: null), author: Chen Chen